Control network management system

ABSTRACT

A control network management system for relaying first and second wireless communications comprises a first repeater having a packet control means for writing priority information in a header of communication packet data of the first wireless communication, as received and transmitting the communication packet data with a hash value of the header, added thereto, a second repeater having a packet control means for zero-clearing priority information in a header of communication packet data of the second wireless communication, as received, or changing the priority information to a predetermined value before transmitting the communication packet data with a hash value of the header, added thereto, and a third repeater having a priority control means for applying priority control to the header of the communication packet data received from the first repeater or the second repeater, on the basis of priority information, thereby transmitting the communication packet data to a control system.

This application claims priority from Japanese Patent Application No.2010-001205, filed on Jan. 6, 2010, the entire contents of which areherein incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a control network management system forrelaying a first wireless communication in conformity with IP (InternetProtocol) and a process control wireless communication standard, and asecond wireless communication in conformity with IP and a wirelesscommunication standard differing from the process control wirelesscommunication standard, and in particular, to a control networkmanagement system capable of avoiding tampering, and so forth, attemptedby a mala fide third party, and allowing a signal of a process controlwireless communication of which highly real-time responsiveness isrequired while guaranteeing priority, and a signal of which real timeresponsiveness is not required so much to coexist in the same network.

2. Related Art

It has since been proposed that a process control system in, forexample, industrial automation is constituted as a wireless controlnetwork system making use of wireless communication.

The reason for this is that since a related-art control system isconfigured as a wired network, it has been impossible to install fielddevices such as sensors for measuring temperature, a flow rate, and soforth, respectively, at optimum locations inside a plant owing tolimitations to a communication distance, constraints to routing ofwiring, and so forth, resulting in deterioration in control accuracy,and the wireless control network system is therefore proposed in orderto obviate such inconvenience.

Further, there has been proposed a control network management system forcontrolling the operation of the wireless control network system, andoptimizing the operation of a plant in whole.

The field devices include various field devices such as, for example, adifferential pressure gage, a flow meter, a thermometer, a monitoringcamera, an actuator, a controller, and so forth.

There has lately been seen a move for attempting to incorporate wirelesstechnologies into various industrial sectors including a process controlsector, and wireless communication standards as well have been understudies. More specifically, under study at present are Wireless HARTprovided under HART (Highway Addressable Remote Transducer) 7, and aprocess control wireless communication standard ISA100. 11a, approved byISA 100 committee of ISA (International Society of Automation). TheWirelessHART, and ISA100. 11a each are a protocol/standard of industrialwireless communication for execution of frequency divisioncommunication, and the contents of arrangements concerning respectivecommunications are explained in, for example, the following documents;

-   Document 1: Wireless systems for industrial automation: Process    control and related applications-   Document 2: Control with WirelessHART (URL: http://www.hartcom.    org/protocol/training/resources/wiHART_resources/Control_with_wirelessH    ART.pdf)

The WirelessHART, and ISA100. 11a are adopted for a wireless controlnetwork system in conformity with IEEE (Institute of Electrical andElectronic Engineers) 802. 15. 4, where a large number of field devicesare installed by taking advantage of small size • and power-savingfeature of the respective field devices.

Meanwhile, there has also been proposed a wireless communication systemmaking use of “Wi-Fi (Wireless Fidelity)” technology (hereinafterreferred to as Wi-Fi wireless communication) in conformity with IEEE802. 11a/IEEE 802. 11b since some time ago.

As the Wi-Fi communication, there has been proposed a wirelesscommunication system in a process control system, connected with amaintenance terminal for a maintenance operation by a worker on a jobsite, and field devices such as a monitoring camera of whichcommunication of massive date (for example, statistical data, a movingpicture screen, a still picture screen, various image data, and soforth) is required.

For some time up to now, there have been under study a repeater forcontrolling the operation of a wireless control network system by makinguse of both wireless communication in conformity with the WirelessHART,ISA100. 11a, and wireless communication in conformity with the Wi-Ficommunication to thereby relay both the communications in order tooptimize the operation of a plant as a whole, and a control networkmanagement system using the repeater.

For example, U.S. Patent Application No. 20070268884A relates to arelated-art network management system.

The above U.S. patent application features a technology concerning amechanism for a wireless system for execution of frequency hopping,being compatible with a Wi-Fi wireless communication system, using acommunication frame, wherein respective communication time zones of boththe systems are divided from each other, thereby providing a guardinterval (blank time for prevention of interference) therebetween.

In the above related-art control network management system, highlyreal-time responsiveness (for example, response within 10 ms, and soforth) is required of the process control wireless communication (thewireless communication in conformity with the WirelessHART and ISA100.11a, respectively) in order to execute transmit/receive of variouscontrol data (a flow rate, a pressure value, and so forth) necessary forcarrying out an optimum operation of a plant and so forth.

On the other hand, real-time responsiveness higher than that required inthe case of the WirelessHART and ISA100. 11a is not required of theWi-Fi wireless communication.

With the related-art control network management system, however, therehas existed a problem in that even if priority control is applied to theprocess control wireless communication among the process controlwireless communication, and the Wi—Fi wireless communication in order tosecure the quality of the process control wireless communication ofwhich particularly high real-time responsiveness is required, there is apossibility that communication according to priority cannot be executeddue to information for deciding priority being intercepted by a malafide third party to be thereby subjected to tampering because anyone cangain access to the relevant wireless communication. This problem isspecifically described hereunder.

For some time up to now, there has been under study a repeater forrealizing a mechanism wherein a wireless network system of the processcontrol wireless communication, of which the highly real-timeresponsiveness is required, is compatible with the Wi-Fi wirelesscommunication system of which the real-time responsiveness higher thanthat required in the case of the process control wireless communicationis not required, and a control network management system using therepeater.

With the related-art technology, in particular, there has been understudy use of a priority control function, generally called QoS (Qualityof Service), as a function mounted in a repeater, such as a router, aLAN switch, and so forth, in order to secure the quality of the processcontrol wireless communication more important than the Wi-Fi wirelesscommunication.

More specifically, a method whereby a repeater decides priority includesa method for a repeater explicitly designating priority by making use ofa field prepared in the header of communication packet data.

For example, relatively high priority information is written in a TOS(Type of Service) field, or a DSCP (Differentiated Services Code Point)field of an IP (Internet Protocol) packet by terminals or field devices,making up a network, whereupon a repeater executes prioritization on thebasis of the priority information (TOS, or DSCP).

For example, when any of a plurality of terminals making up a network,or any of a plurality of field devices making up a network preparescommunication packet data relating to data of high real-timecharacteristic, such as voice communication data, or process controldata (control data such as pressure, a flow rate, and so forth), arepeater writes priority information in the TOS field, or the DSCPfield, prepared in the header (IP Header) of packet data incommunications in conformity with IP.

The repeater controls transmission timing of the packet data on thebasis of the priority information written in the TOS field, or the DSCPfield, prepared in the IP Header of the communication packet datareceived from the terminal, or the field device.

That is, the repeater transmits the communication packet data asreceived, in order of decreasing precedence. Even if packets lower inprecedence build up internally (in a storage means), the repeater sendsthem out in order of decreasing precedence on the basis of the priorityinformation.

As a result, with the related-art control network management system, ithas been possible to provide high quality communications of whichrelatively high real-time responsiveness is required by the action ofthe repeater, for explicitly designating priority, making use of fieldsprepared in the header of the communication packet data, in the methodfor the repeater deciding priority.

FIGS. 3(A), 3(B) each are a schematic representation showing a format ofrelated-art communication packet data, in which FIG. 3(A) is theschematic representation showing the communication packet data in whole,and FIG. 3(B) is the schematic representation for explaining about an IPheader thereof. In FIG. 3(A), the communication packet data is made upof a TOS field, a DSCP field, an IP header, and IP data, and as shown inFIG. 3(B), the IP header is provided with the TOS field corresponding to1 octet.

With the related-art control network management system described asabove, however, even if the priority control is executed in order tosecure high real-time responsiveness of the process control wirelesscommunication, a problem has existed in that there is a possibility thatcommunications according to priority cannot be implemented becauseanyone can gain access to the relevant wireless communication, and thewireless communication is intercepted by a mala fide third party, andinformation for deciding priority is subjected to tampering.

More specifically, with the related-art control network managementsystem, in the case of executing the priority control on the assumptionthat the Wi-Fi wireless communication, and the process control wirelesscommunication (signals thereof) are allowed to coexist in the samenetwork without any countermeasures taken into consideration, if, forexample, the communication packet data of the process control wirelesscommunication is intercepted by a mala fide third party who has invadedfrom the Wi-Fi wireless communication to be re-transmitted after aportion expressing a priority {TOS (Type of Service) corresponding to 1octet, in (FIG. 3B)} of the communication packet data have beensubjected to tampering, this will cause communication packet data to betransmitted on the basis of priority information after the tampering,thereby causing a problem that security on priority is not provided atall, and it is impossible to carry out the optimal operation of a targetfor control, in a plant, and so forth,

In other words, a problem has existed in that there is a possibility ofthe system being under a replay attack that is an attack techniquewhereby a third party eavesdrops on contents of the communication, andtransmits contents identical to the contents of the communication packetdata of the process control wireless communication, thereby gaining anirregular access.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention address the abovedisadvantages and other disadvantages not described above. However, thepresent invention is not required to overcome the disadvantagesdescribed above, and thus, an exemplary embodiment of the presentinvention may not overcome any disadvantages.

It is one of illustrative aspects of the present invention to solvethose problems, and to realize a control network management systemcapable of avoiding tampering, and so forth, attempted by a mala fidethird party, in particular, and allowing a signal of a process controlwireless communication of which highly real-time responsiveness isrequired while guaranteeing priority, and a signal of which real timeresponsiveness is not required so much to coexist on the same network.

According to one or more illustrative aspects of the invention, there isprovided the control network management system for relaying a firstwireless communication in conformity with IP (Internet Protocol) and aprocess control wireless communication standard, and a second wirelesscommunication in conformity with IP, and a wireless communicationstandard differing from the standard, the control network managementsystem comprising a first repeater having a packet control means forwriting priority information in a header of communication packet data ofthe first wireless communication, as received and transmitting thecommunication packet data with a hash value of the header, addedthereto, a second repeater having a packet control means forzero-clearing part, or a whole of priority information in a header ofcommunication packet data of the second wireless communication, asreceived, or changing the priority information to a predetermined valuebefore transmitting the communication packet data with a hash value ofthe header, added thereto, and a third repeater having a prioritycontrol means for applying priority control to the header of thecommunication packet data received from the first repeater or the secondrepeater, on the basis of priority information, thereby transmitting thecommunication packet data to a control system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one embodiment of a control networkmanagement system according to the invention;

FIG. 2 is a schematic diagram for explaining about operation of thecontrol network management system according to the invention; and

FIGS. 3(A), 3(B) each are a schematic representation showing a format ofrelated-art communication packet data.

DEAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A control network management system according to the invention has afeature in that the control network management system is provided with afirst repeater comprising a packet control means for writing priorityinformation on a header of communication packet data of a processcontrol wireless communication (hereinafter referred to as a firstwireless communication), such as mainly, WirelessHART, ISA100. 11a, andso forth, thereby transmitting the communication packet data with a hashvalue of the header, added thereto, a second repeater comprising apacket control means for zero-clearing a part, or the whole of priorityinformation in the header of communication packet data of communicationof the Wi-Fi communication • other than the process control wirelesscommunication, or changing the same to a predetermined value beforetransmitting the communication packet data with a hash value of theheader, added thereto, and a third repeater comprising a prioritycontrol means for applying priority control to headers of respectivecommunication packet data blocks received from the first repeater or thesecond repeater on the basis of the priority information, therebytransmitting communication packet data to a control system.

FIG. 1 is a block diagram showing one embodiment of a control networkmanagement system according to the invention. In FIG. 1, the controlnetwork management system according to the invention is comprised mainlyof wireless nodes 11 to 15, each thereof, being a field device having asensor function for measuring a physical quantity, such as, for example,temperature, a flow rate, and so forth, or an actuator function forcontrolling a control valve, further the field device representing oneexample of a plurality of first wireless communication terminals, havinga wireless communication function for wireless transfer of variousmeasurement data blocks through wireless communications according to thecommunication standard ISA100. 11a (or WirelessHART), a gateway(hereinafter referred to as GW) 2, representing one example of a firstrepeater for transferring the respective communication packet datablocks received from the wireless nodes 11 to 15, wireless nodes 31 to35 (in the figure, shown as Wi-Fi nodes), each thereof, being a fielddevice, such as a maintenance terminal for maintenance work to beperformed by a worker at a job site, a monitoring camera of whichcommunication of massive data (for example, statistical data, a movingimage, a still image, various image data blocks, and so forth) isrequired, and so forth, further the field device representing oneexample of a plurality of second wireless communication terminals,having wireless communication function for wireless transfer of variousmeasurement data blocks • voice data blocks through the Wi-Fi wirelesscommunication, an access point (hereinafter referred to as AP) 4representing one example of a second repeater for transferring therespective communication packet data blocks received from the wirelessnodes 31 to 35, a QoS (Quality of Service) server 5 representing oneexample of a third repeater such as a router, a switch, and so forth,for executing communications with the GW2, and the AP4, and applyingpriority control to the respective communication packet data blocks asreceived before relaying (transferring), a network 100 for wirelesstransfer of the communication packet data blocks, such as the variousmeasurement data blocks, the control data locks, and so forth, by theWi-Fi wireless communication, and a QoS server 6 representing oneexample of a fourth repeater, such as a router, a switch, and so forth,for applying priority control to the communication packet data blocksreceived via the network 100 before relaying (transferring) to a controlsystem 200.

Wireless communications in conformity with IP and the process controlwireless communications standard (ISA100. 11a or WirelessHART), ishereinafter referred to as the first wireless communication, whilewireless communications in conformity with IP and wirelesscommunications standard (the Wi-Fi wireless communication, and so forth)differing from the process control wireless communications standard ishereinafter referred to as the second wireless communication.

The wireless nodes 11 to 15 each are a field device having the sensorfunction for measuring the physical quantity, such as temperature, aflow rate, and so forth, or the actuator function for controlling acontrol valve, for executing transmit/receive of the various measurementdata blocks on the basis of a predetermined control process according toISA100. 11a as one example of the process control wireless communicationstandard, and so forth.

Those wireless nodes 11 to 15 each execute the first wirelesscommunication in conformity with IP (Internet Protocol), and the processcontrol wireless communication standard, thereby constructing a wirelesscontrol network system such as a wireless sensor network, and so forthvia, for example, an access point (not shown).

More specifically, the wireless nodes 11 to 15 each comprise acommunication means for transmitting measurement data • process controldata, as measured by itself, or executing transmit/receive of respectivecommunication packet data blocks of the first wireless communication,received from other wireless nodes 11 to 15, via wireless communication,an arithmetic and control means such as a CPU for controlling thewireless node in whole, thereby causing the wireless node to operate asa field device, and transmitting the measurement data • process controldata, as obtained, or the respective communication packet data blocksreceived from the other wireless nodes to the GW2, and a storage meanssuch as, for example, a RAM, a ROM, and so forth, for storing variousinformation, such as an OS, in the main, a program, and an applicationfor running the wireless nodes 11 to 15, respectively, path information(network information such as IP address, MAC address, and so forth) on apath of data in use upon the execution of the program, and so forth,from the wireless node itself to the other wireless nodes 11 to 15, GW2,and so forth respectively.

The GW2 comprises a packet-control means 21 for writing priorityinformation in the header of a communication packet data block of thefirst wireless communication, received from any of the wireless nodes 11to 15, thereby transmitting the communication packet data block with ahash value of the header, added thereto, a wireless communication meansfor executing transmit/receive of the communication packet data blocksof the first wireless communication via the wireless nodes 11 to 15,respectively, and wireless communication, a communication means forexecuting transmit/receive of the communication packet data of the firstwireless communication with the QoS server 5, an arithmetic and controlmeans such as a CPU for controlling the GW2 in whole, and transferringthe respective communication packet data blocks received from thewireless nodes 11 to 15, respectively, to the QoS server 5, and astorage means, such as a RAM, a ROM, and so forth, for storing variousinformation, such as the OS, in the main, a program, and an applicationfor running the GW2, and path information (network information such asthe IP address, MAC address, and so forth) on a path of data in use uponthe execution of the program, and so forth, from the GW2 itself up tothe wireless nodes 11 to 15, respectively, and the QoS server 5, and soforth.

Further, the GW2 may comprise, in addition to the configuration thereof,described as above, a time-stamp control means 22 for, upon receiving acommunication packet data block of the first wireless communication,adding a time-stamp field to the header of the communication packet datablock to write a time-stamp therein.

Furthermore, the packet-control means 21 of the GW2 may, in addition tothe configuration thereof, described as above, recalculate a checksum ofthe header of the communication packet data block of the first wirelesscommunication to be written in the header of the communication packetdata block.

The wireless nodes 31 to 35 each are a field device, such as, forexample, the maintenance terminal for maintenance work to be performedby a worker at a job site, the monitoring camera of which communicationof massive data (for example, statistical data, a moving image, a stillimage, various image data blocks, and so forth) is required, and soforth, having a wireless communication function for wireless transfer ofthe various measurement data blocks through the Wi-Fi wirelesscommunication.

Those wireless nodes 31 to 35 each are the field device, such as forexample, the maintenance terminal for maintenance work to be performedby a worker at a job site, the monitoring camera of which communicationof massive data (for example, statistical data, a moving image, a stillimage, various image data blocks, and so forth) is required, a computerfor executing, for example, voice communication, and so forth, thewireless nodes 31 to 35 executing the second wireless communication inconformity with IP, and the wireless communication standard differingfrom the first wireless communication standard, such as the Wi-Fiwireless communication, and so forth, thereby constructing a wirelessnetwork via an access point (not shown), and so forth.

More specifically, the wireless nodes 31 to 35 each comprise acommunication means for transmitting the massive data, such as thestatistical data, the moving image, the still image, the various imagedata blocks, and so forth, or executing transmit/receive of respectivecommunication packet data blocks of the second wireless communication,from other wireless nodes 31 to 35, via wireless communication, anarithmetic and control means such as a CPU for controlling the wirelessnode in whole, and transmitting the massive data, such as thestatistical data, the moving image, the still image, the various imagedata blocks, and so forth, or the respective communication packet datablocks received from other wireless nodes, respectively, to the AP4, anda storage means such as, for example, a RAM, a ROM, and so forth, forstoring various information, such as the OS, in the main, a program, andan application for running the wireless nodes 31 to 35, respectively,path information (network information such as the IP address, MACaddress, and so forth) on a path of data in use upon the execution ofthe program, and so forth, from the field device itself up to otherwireless nodes, respectively, the AP4, and so forth.

The AP4 comprises a packet-control means 41 for zero-clearing part orthe whole of priority information on the header of a communicationpacket data block of the second wireless communication, received fromany of the wireless nodes 31 to 35, to (00000000), or changing the sameto a predetermined value (00000001, and so forth), and adding a hashvalue of the header to the communication packet data block beforetransmission, a wireless communication means for executingtransmit/receive of the communication packet data blocks of the firstwireless communication via the wireless nodes 31 to 35, respectively,and wireless communication, a communication means for executingtransmit/receive of the communication packet data of the first wirelesscommunication with the QoS server 5, an arithmetic and control meanssuch as a CPU for controlling the AP4 in whole, and transferring therespective communication packet data blocks received from the wirelessnodes 31 to 35, respectively, to the QoS server 5, and a storage means,such as, for example, a RAM, a ROM, and so forth, for storing variousinformation, such as the OS, in the main, a program, and an applicationfor running the repeater as the AP4, and path information (networkinformation such as IP address, MAC address, and so forth) on a path ofdata in use upon the execution of the program, and so forth, from theAP4 itself up to the wireless nodes 31 to 35, respectively, and the QoSserver 5, and so forth.

Meanwhile, the packet-control means 41 of the AP4 may change thepriority information in the header of the communication packet datablock of the second wireless communication to information lower inpriority than the priority information written in the header of thecommunication packet data block by the packet-control means 21 of theGW2.

Further, the packet-control means 41 of the AP4 may, in addition to theconfiguration thereof, described as above, recalculate a checksum of theheader of the communication packet data block of the second wirelesscommunication to be written in the header of the communication packetdata block.

Furthermore, the AP4 may, in addition to the configuration thereof,described as above, comprise a time-stamp control means 42 for, uponreceiving the communication packet data block of the second wirelesscommunication, adding a time-stamp field to the header of thecommunication packet data block, and writing a time-stamp therein.

The QoS server 5 comprises a communication means for executingtransmit/receive of communication packet data with the GW2, or the AP4,a wireless communication means for executing transmit/receive ofcommunication packet data with the QoS server 6 via the network 100, apriority-control means 51 for applying priority control to the header ofthe communication packet data received from the GW2, or the AP4, on thebasis of the priority information, thereby controlling the communicationmeans before transmitting the communication packet data to the controlsystem 200, an arithmetic and control means such as a CPU forcontrolling the QoS server 5 in whole, and applying priority control tothe header of the communication packet data received from the GW2, orthe AP4, by use of the priority-control means, before transferring thecommunication packet data to the QoS server 6, and a storage means suchas, for example, a RAM, a ROM, and so forth, for storing variousinformation, such as the OS, in the main, a program, and an applicationfor running the repeater as the QoS server 5, path information (networkinformation such as the IP address, MAC address, and so forth) on a pathof data in use upon the execution of the program, and so forth, from theQoS server itself up to the GW2, or the AP4, the network 100, the QoSserver 6, and so forth.

Further, the QoS server 5 may, in addition to the configuration thereof,described as above, comprise a correctness-inspection means 52 forinspecting correctness on the basis of a hash value of communicationpacket data received from the GW2, or the AP4, and controlling thecommunication means, thereby transmitting correct communication packetdata to the control system 200.

Further, the QoS server 5 may, in addition to the configuration thereof,described as above, comprise a time-stamp control means 53 for, uponreceiving communication packet data, adding a time-stamp field to theheader of the communication packet data, and writing a time-stamp istherein. In this case, the correctness-inspection means 52 may inspectcorrectness depending on whether or not the communication packet data isreceived by the QoS server 5 itself after a lapse of predetermined timefrom a time stamp in the communication packet data as received.

Still further, the arithmetic and control means of the QoS server 5 may,in addition to the configuration thereof, described as above,recalculate a checksum of the header of the communication packet datareceived from the GW2, or the AP4 to be written in the header of thecommunication packet data.

The QoS server 6 comprises a wireless communication means for executingtransmit/receive of communication packet data from the QoS server 5 viathe network 100, a communication means for executing transmit/receive ofthe communication packet data with the control system 200, apriority-control means 61 for applying priority control to the header ofthe communication packet data received from the QoS server 5 via thenetwork 100, on the basis of priority information, thereby controllingthe communication means before transmitting the communication packetdata to the control system 200, an arithmetic and control means such asa CPU for controlling the QoS server 6 in whole, and applying prioritycontrol to the header of the communication packet data received from theQoS server 5 via the network 100, by use of the priority-control means,before transferring the communication packet data to the control system200, and a storage means, such as, for example, a RAM, a ROM, and soforth, for storing various information, such as the OS, in the main, aprogram, and an application, for running the repeater as the QoS server6, path information (network information such as the IP address, MACaddress, and so forth) on a path of data in use upon the execution ofthe program, and so forth, from the QoS server 6 itself up to thenetwork 100, the control system 200, and so forth, respectively.

Meanwhile, the QoS server 6 may, in addition to the configurationthereof, described as above, comprise a correctness-inspection means 62for inspecting correctness on the basis of a hash value, or a checksumof respective communication packet data blocks received from the QoSserver 5 via the network 100, and controlling the communication means,thereby transmitting correct communication packet data to the controlsystem 200.

Further, the QoS server 6 may, in addition to the configuration thereof,described as above, comprise a time-stamp control means 63 for, uponreceiving communication packet data, adding a time-stamp field to theheader of the communication packet data, and writing a time-stamptherein. In this case, the correctness-inspection means 62 may inspectcorrectness depending on whether or not the communication packet data isreceived by the QoS server 6 itself after a lapse of predetermined timefrom a time stamp in the communication packet data as received.

Still further, the arithmetic and control means of the QoS server 6 may,in addition to the configuration thereof, described as above,recalculate a checksum of the header of the communication packet datareceived from the QoS server 6 via the network 100 to be written in theheader of the relevant communication packet data.

The network 100 is comprised of a terminal, or a repeater, an accesspoint, and so forth (such field devices are not shown), for executingwireless communication by Wi-Fi, or WiPax, and so forth, the network 100being coupled with the QoS server 5, and the QoS server 6, therebyexecuting transmit/receive (relay) of communication packet data.

The control system 200 executes collection • monitoring of sensor datafrom each of the wireless nodes 11 to 15, and an operation of anactuator, and as an example of the control system 200, there is cited aninstrumentation system containing DCS (Distributed Control Systems). Thecontrol system 200 may be of any specific configuration provided that itis capable of controlling the wireless nodes, and monitoring processcontrol, and measurement data in a wireless control network managementsystem.

The control system 200 may have a system configuration comprised of, forexample, a plurality of networks disjoined from each other at Level 1,Level 2, Level 3, Level 3. 5, and Level 4, respectively, as shown inFIG. 1.

In this case, the network at Level 1 is a control network composed offield devices comprising a sensor function for measuring a physicalquantity such as temperature, a flow rate, and so forth, or an actuatorfunction for controlling a control valve, and so forth, the controlnetwork executing transmit/receive of various measurement data blocks •control data blocks.

The network at Level 2 is a control network made up of a plurality offield devices such as controllers for controlling the field devices,such as a valve, a control valve, and so forth, making up the network atLevel 1. The controllers each are connected to the network at Level 1 toreceive the various measurement data blocks from the field devicesmaking up the network at Level 1. Further, when control data transmittedfrom the controller is inputted to the respective field devices makingup the network at Level 1, the respective field devices operate on thebasis of the control data (for example, the controller is caused toadjust the opening thereof).

The network at Level 3 is connected to the network at Level 2 vialayer-2 switches, being composed of a plurality of control servers foraccumulating • storing the various measurement data blocks and controldata blocks, received from the respective controllers, the controlservers grasping long term trends of the various data blocks.

The network at Level 3. 5 is a DMZ (Demilitarized Zone) that isconnected to the network at Level 3 via a layer-2 switch, and a firewalldevice, representing an area isolated from external networks, andinternal networks, respectively, by means of a firewall. In FIG. 1, thenetwork at Level 3. 5 is connected to the QoS server 6 to be furtherconnected to the QoS server 5, the AP4, and the GW2, respectively, viathe network 100, as one embodiment of the invention.

The network at Level 4 is a control • management network composed of aplurality of control servers for controlling a wireless sensor networkmade up of the wireless nodes 11 to 15, and so forth, the network atLevel 4 being connected to the network at Level 3. 5 (DMZ) via a layer-3switch, a firewall device, and so forth.

The respective control servers of the control • management network arecapable of transmitting control data to at least any of the wirelessnodes 11 to 15, as a target for control, via the DMZ, the QoS server 6,the QoS server 5, and the GW2, on the basis of communication packet datareceived from any of the wireless nodes 11 to 15 via the QoS server 5,the network 100, the QoS server 6, and the DMZ, in order to control thewireless nodes 11 to 15, respectively, as necessary.

(Explanation about Operation)

A control network management system according to the invention,configured as above, can execute, for example, operations described asfollows. FIG. 2 is a schematic diagram for explaining about operation ofthe control network management system according to the invention, andthe operation is described by referring to operation steps taken insuccession from steps (1-1) to (1-10), as depicted in FIG. 2.

(1-1)

The packet-control means 41 of the AP4, upon receiving communicationpacket data of the second wireless communication, from any of thewireless nodes 31 to 35, via the communication means, zero-clears partor the whole of information (TOS information) in the TOS field in theheader of the communication packet data, as received (to, for example,00000000), or changes the same to a predetermined value (00000001),recalculating a checksum of a 16-bits header in the IP header to bewritten in the header of the communication packet data.

Further, the packet-control means 41 of the AP4, upon receiving of thecommunication packet data of the second wireless communication, from anyof the wireless nodes 31 to 35, may duplicate the communication packetdata, in which case, priority information is written in the TOS field inthe header of the communication packet data as duplicated, and thechecksum of the 16-bits header in the IP header is recalculated to bewritten in the header of the communication packet data, as duplicated.

Still further, the packet-control means 41 of the AP4 may change thepriority information written in the TOS information in the header of thecommunication packet data of the second wireless communication topriority information lower in priority than the priority informationwritten in the header of the communication packet data by thepacket-control means 21 of the GW2.

Further, the packet-control means 41 of the AP4 may execute right-shiftof leading 4-bits out of TOS information 8-bits in the header by 4-bitsto thereby zero clear the leading 4-bits.

By so doing, the QoS server 5 is able to handle the communication packetdata of the first wireless communication, transmitted from the GW2, asthe communication packet data higher in priority than the communicationpacket data transmitted from the AP2, so that this is effective in thata signal of the process control wireless communication of which highlyreal-time responsiveness is required while guaranteeing priority, and asignal of which real time responsiveness is not required so much areallowed to coexist on the same network.

(1-2)

The time-stamp control means 42 of the AP4 adds a time-stamp field fromoctet 24 to 27 to be written in the header of the communication packetdata block (or the communication packet data block as duplicated),thereby writing 32-bits time-stamp therein.

In other words, the time-stamp control means 42 of the AP4 newlyprepares a time-stamp field in (the header) of the communication packetdata of the second wireless communication, received from any of thewireless nodes 31 to 35, thereby writing a time-stamp therein.

(1-3)

The packet-control means 41 of the AP4 calculates a hash value (fromoctet 0 to 27) in the header of the communication packet data block (orthe communication packet data block as duplicated).

(1-4)

The packet-control means 41 of the AP4 adds the hash value as calculatedto the communication packet data block (or the communication packet datablock as duplicated) to be transmitted to the QoS server 5.

More specifically, the packet-control means 41 of the AP4 newly preparesa hash-value field in (the header of) the communication packet datablock of the second wireless communication received from any of thewireless nodes 31 to 35, and writes a hash value as calculated thereinbefore transmitting the communication packet data block to the QoSserver 5.

That is, upon receiving the communication packet data block of thesecond wireless communication from any of the wireless nodes 31 to 35,the packet-control means 41 of the AP4 adds new information (atime-stamp field, a hash-value field, and TOS priority information) intothe header of the communication packet data to be transmitted to the QoSserver 5.

(1-5)

The packet-control means 21 of the GW2, upon receiving communicationpacket data of the first wireless communication from any of the wirelessnodes 11 to 15 via the communication means, writes priority informationin the TOS field in the header of the communication packet data asreceived, and recalculates a checksum of a 16-bits header in the IPheader to be written in the header of the relevant communication packetdata block.

Meanwhile, the packet-control means 21 of the GW2, upon receivingcommunication packet data of the second wireless communication from anyof the wireless nodes 11 to 15, may duplicate the relevant communicationpacket data, in which case, priority information may be written in theTOS field in the header of the communication packet data as duplicated,and a checksum of a 16-bits header in the IP header is recalculated tobe written in the header of the relevant communication packet data.

Herein, the packet-control means 21 of the GW2 writes bits higher inpriority than bits written in the AP4, in the TOS field in the header ofthe communication packet data of the second wireless communication,however, assuming that priority is expressed by, for example, theleading 4-bits out of TOS information 8-bits in the header, lower 4-bitsmay be zero cleared.

(1-6)

A time-stamp control means 22 of the GW2 adds a time-stamp field fromoctet 24 to 27 in the header of the communication packet data block (orthe communication packet data block as duplicated), thereby writing32-bits time-stamp therein.

In other words, the time-stamp control means 22 of the GW2 newlyprepares a time-stamp field in (the header) of communication packet dataof the first wireless communication, received from any of the wirelessnodes 11 to 15, thereby writing a time-stamp therein.

(1-7)

The packet-control means 21 of the GW2 calculates a hash value (fromoctet 0 to 27) in the header of the communication packet data block (orthe communication packet data block as duplicated).

More specifically, the packet-control means 21 of the GW2 newly preparesa hash value field in (the header) of the communication packet data ofthe second wireless communication, from any of the wireless nodes 31 to35, having received a signal, thereby writing a calculated hash valuetherein to be transmitted to the QoS server 5.

(1-8)

The packet-control means 21 of the GW2 adds the calculated hash value tothe communication packet data block (or the communication packet datablock as duplicated) to be transmitted to the QoS server 5.

More specifically, the packet-control means 21 of the GW2, uponreceiving the communication packet data of the first wirelesscommunication from any of the wireless nodes 11 to 15, adds newinformation (the time-stamp field, the hash value field, the priorityinformation in the TOS field) into the header of the relevantcommunication packet data to be transmitted to the QoS server 5.

The sequence of respective operations in the steps (1-1) to (1-4), andthe sequence of respective operations in the steps (1-5) to (1-8) arenot limited to the forgoing example.

(1-9)

The priority-control means 51 of the QoS server 5 applies prioritycontrol to the header of communication packet data received from theGW2, or the AP4, via the communication means, on the basis of thepriority information, controlling the communication means according toan output queue of the packet data as received, thereby transmitting apacket higher in priority to the QoS server 6 via the network 100.

Further, in addition to this operation, the correctness-inspection means52 of the QoS server 5 may compare a hash value of communication packetdata received from the GW2, or the AP4, with a hash value worked outfrom the relevant communication packet data with the use of a hashfunction provided in advance, thereby inspecting correctness dependingon whether or not the respective hash values match each other, and ifso, the correctness-inspection means 52 may decide the communicationpacket data as correct, thereby controlling the communication means, andtransmitting correct communication packet data to the QoS server 6 viathe network 100.

Still further, in addition to the operation described as above, thecorrectness-inspection means 52 of the QoS server 5 may write a 32-bitstime stamp in the time-stamp field in the header of the communicationpacket data (or the communication packet data as duplicated),

Yet further, in addition to the operation described as above, thecorrectness-inspection means 52 of the QoS server 5 may compare achecksum of communication packet data, written in the header of thecommunication packet data of the respective wireless communications, asreceived, with a checksum newly worked out from the relevantcommunication packet data, thereby inspecting matching property of thecommunication packet data, depending on whether or not the respectivechecksums match each other, and if so, the correctness-inspection means52 may decide that the matching property is obtained, therebytransmitting the communication packet data having the matching property,to the QoS server 6 via the network 100.

Furthermore, in addition to the operation described as above, thecorrectness-inspection means 52 of the QoS server 5 may inspectcorrectness on the basis of a time-stamp written in the communicationpacket data of the wireless communication, received from the GW2, or theAP4, depending on whether or not the communication packet data isreceived by the QoS server 5 itself after a lapse of predetermined timefrom the time stamp in the communication packet data, as received, andif it is received within the predetermined time, thecorrectness-inspection means 52 may decide that the communication packetdata is correct, thereby transmitting correct communication packet datato the QoS server 6 via the network 100.

(1-10)

The priority-control means 61 of the QoS server 6 applies prioritycontrol to the header of communication packet data received from the QoSserver 5 via the network 100, on the basis of priority information,controlling the communication means according to an output queue of thepacket as received, thereby transmitting communication packet datahigher in priority to a control system.

For example, the priority-control means 61 of the QoS server 6 appliespriority control to the headers of respective communication packet datareceived from the QoS server 5 via a communication means (not shown)before transmitting the respective communication packet data to the DMZof the control system.

The communication packet data from the QoS server 6 is transferred tothe control • management network depicted at Level 4 via DMZ. Therespective control servers that male up the control • management networktransmit control data to at least any of the wireless nodes 11 to 15, asthe target for control, via DMZ, the QoS server 6, the QoS server 5, andthe GW2, on the basis of the communication packet data as received, inorder to control the wireless nodes 11 to 15, respectively, asnecessary.

Further, in addition to the operation in the step (1-10) as above, thecorrectness-inspection means 62 of the QoS server 6 may compare a hashvalue of respective communication packet data received from the QoSserver 5 with a hash value worked out from the relevant communicationpacket data block with the use of the hash function provided in advance,thereby inspecting correctness depending on whether or not therespective hash values match each other, and if so, thecorrectness-inspection means may decide the communication packet data ascorrect, thereby controlling the communication means, and transmittingcorrect communication packet data to the control system.

For this reason, the present invention is effective in that thecorrectness of the communication packet data is inspected on the basisof the hash value of the respective communication packet data receivedby the correctness-inspection means of the QoS server 6, and the correctcommunication packet data is transmitted to the control system bycontrolling the communication means, thereby enabling tampering, and soforth, by a mala fide third party, to be avoided.

Further, in addition to the operation in the step (1-10) as above, thetime-stamp control means 62 of the QoS server 6 may write a 32-bitstime-stamp in the time-stamp field in the header of the communicationpacket data block (or the communication packet data block asduplicated).

Still further, in addition to the operation described as above, thecorrectness-inspection means 62 of the QoS server 6 may compare achecksum of communication packet data, written in the header of thecommunication packet data of the respective wireless communications, asreceived, with a checksum newly worked out from the relevantcommunication packet data, thereby inspecting matching properties of therespective checksums, depending on whether or not the respectivechecksums match each other, and if so, the correctness-inspection means62 may decide that the matching property is obtained, therebytransmitting the communication packet data having the matching property,to the control system.

In addition to the operation described as above, thecorrectness-inspection means 62 of the QoS server 6 may inspectcorrectness depending on whether or not communication packet data isreceived by the QoS server 6 itself after a lapse of the predeterminedtime from the time stamp in the communication packet data as received,on the basis of the time stamp written in the communication packet dataof the wireless communication, received from the QoS server 5, and if itis received within a predetermined time, the correctness-inspectionmeans 62 may decide that the communication packet data is correct,thereby transmitting correct communication packet data to the controlsystem.

Further, with the network 100 for transferring communication packet databetween the QoS server 5, and the QoS server 6, all the repeaters (notshown), such as a router, a switch, and so forth, making up the network100, may check TOS, a hash value, and a time stamp, and such aconfiguration as above is effective in that guarantee of the prioritycontrol function QoS is further enhanced.

As a result, the control network management system according to theinvention is provided with the first repeater having the packet controlmeans for writing priority information on the header of communicationpacket data of the first wireless communication, as received, andtransmitting the communication packet data with the hash value of theheader, added thereto, the second repeater having the packet controlmeans for zero-clearing part, or the whole of the priority informationin the header of communication packet data of the second wirelesscommunication, as received, or changing the priority information to thepredetermined value before transmitting the communication packet datawith the hash value of the header, added thereto, and the third repeaterhaving the priority control means for applying the priority control tothe headers of the respective communication packet data received fromthe first repeater, and the second repeater, on the basis of thepriority information, thereby transmitting the communication packet datato the control system 200, so that the system is effective in thattampering, and so forth, by the mala fide third party, is avoided, andthe signal of the process control wireless communication of which highlyreal-time responsiveness is required while guaranteeing priority, andthe signal of which real-time responsiveness is not required so much areallowed to coexist on the same network.

OTHER EMBODIMENTS

Further, with the control network management system according to theinvention, the following operations may be executed in addition to thesteps (1-1) to (1-10) previously explained about under (Explanationabout operation).

For example, with the packet-control means 21 of the GW2, or thepacket-control means 41 of the AP4, calculation of a value from octet 28to 31 may take precedence over other operations.

Further, in this case, as for the initial-value (salt) serving as a basefor working out a hash value with the use of one-way function,authentication of a data source may be executed between the GW2, and thewireless nodes 11 to 15, and between the AP4, and the wireless nodes 31to 35, respectively.

More specifically, the control network management system according tothe invention may be provided with an initial-value master (not shown)for generating the initial-value (salt) to be used in calculating thehash value, thereby distributing the initial-value to respective devicessuch as the GW2, the AP4, the QoS server 5, the QoS server 6, and soforth.

Still further, with the control network management system according tothe invention, the wireless nodes 11 to 15, the GW2, the wireless nodes31 to 35, the AP4, QoS server 5, QoS server 6, and so forth,respectively, may adopt a configuration wherein, for example, a publickey algorithm, digital signature scheme, time-stamp format, andtime-setting scheme (including an error scope), to be used, arepredetermined, and communication is executed in conformity therewith inorder to secure security between propagations of communication packetdata.

The system is effective in that the security between the propagations ofcommunication packet data can be secured by so doing, and as a result,tampering, and so forth, by a mala fide third party, can be avoided.

With such configurations as described above, for example, the followingoperation is executed.

Design • production venders (Va, Vb, Vc, Vd, and so forth) of the GW2,AP4, QoS server 5, and QoS server 6, respectively, prepare a company'spublic keys • secret keys, in pairs, {KP (Va), KP (Vb), KP (Vc), KP(Vd), and so forth}, and the storage means of the GW2, AP4, QoS server5, and QoS server 6, respectively, store those public keys.

Meanwhile, in this case, Va denotes a vender A, Vb denotes a vender B,and so on, while KP (Va) denotes the keys in pairs, of a vender a, KPs(Va) denotes the secret keys of KP (Va), and KPp (Va) denotes the publickeys of KP (Va). That is, KP (Va) is a pair of KPp (Va), and KPs (Va).The same can be said of KP (Vb) to KP (Vd), respectively, however,description thereof is omitted herein.

Those public keys each are signed by a secret key KPs (T) among publickeys in pairs {KP (T), KPp (T), and KPs (T)}, prepared by anauthentication station server managed by a reliable group pre-selectedby the respective venders to be made public in the form of a public keycertificate by the relevant group.

The public keys of the relevant group, and the public key certificate (aself-certificate) are notified to the respective venders via safe paths,not less than two paths (Fax, registered mail, and so forth).

The storage means of the GW2, AP4, QoS server 5, and QoS server 6, andso forth, respectively, store the public key certificate (further, thepublic key certificate may be stored in a smart chip havinganti-tampering characteristics, and so forth).

With the configuration described as above, if the configuration depictedin FIG. 1 is adopted, the respective devices, such as the GW2, the AP4,the QoS server 5, the QoS server 6, and so forth, may be joined with(the network of) the control network management system according to theinvention as follows:

(A) The respective devices, such as the GW2, the AP4, the QoS server 5,the QoS server 6, and so forth, notify information on whether amanufacturer is a company A, or a company B, and so forth, to otherdevices participating in the network of the control network managementsystem through broadcasting, together with the public key certificateand so forth, signed by each device.(B) The device that has received a notification sends back the publickey certificate signed by itself, incorporating the device's owninformation, to the device that has transmitted the notification throughbroadcasting (has introduced itself).(C) A time master (unit) to serve as a time reference in (the networkof) the control network management system, among the devicesparticipating in the network, notifies a signed time of (the network of)the relevant control network management system to the respective devicesthat have joined the system, such as the GW2, the AP4, the QoS server 5,the QoS server 6, and so forth.

By so doing, the respective devices, such as the GW2, the AP4, the QoSserver 5, the QoS server 6, and so forth, making up the control networkmanagement system according to the invention, are able to obtain thepublic keys with a signature of the group mutually reliable from end toend, affixed thereto, thereby setting a time to the time master.

In this connection, the time master is for causing the respectivedevices that participate in the network to set a time at predeterminedintervals, and in particular, for promoting distribution of theinitial-value (salt) for use in working out the hash value for aninitial-value master.

Further, the respective devices may encipher communications between therespective devices on the basis of the public keys of other devicesdeveloped as above, and secret keys, as the public keys in pairs, of therespective devices themselves, stored in the storage means thereof,thereby executing transmit/receive of communication packet data. By sodoing, it is possible to prevent tampering of the header ofcommunication packet data, and a tampering attack on signal priority,thereby forestalling the replay attack (tampering, and so forth,attempted by a mala fide third party, can be avoided), in which respect,the system is effective.

Further, the respective constituent elements of the control networkmanagement system according to the invention may aim at RFI (Request forInformation) under study in WG15 of the ISA standard concerning processcontrol wireless communication {ISA100. 11a concerning process controlwireless communication (Wireless systems for industrial automation:Process control and related applications)}, the respective constituentelements having a function capable of implementing the above-mentioned.

Thus, since the control network management system according to theinvention is provided with the first repeater having the packet controlmeans for writing priority information in the header of thecommunication packet data of the first wireless communication, asreceived, and transmitting the communication packet data with the hashvalue of the header, added thereto, the second repeater having thepacket control means for zero-clearing part, or the whole of priorityinformation in the header of the communication packet data of the secondwireless communication, as received, or changing the priorityinformation to the predetermined value before transmitting thecommunication packet data with the hash value of the header, addedthereto, and the third repeater having the priority control means forapplying priority control to the headers of respective communicationpacket data blocks received from the first repeater, and the secondrepeater, on the basis of the priority information, thereby transmittingthe communication packet data to the control system, it is possible toprevent the tampering on the header of communication packet data, andthe tampering attack on signal priority, thereby forestalling the replayattack (tampering, and so forth, attempted by the mala fide third party,can be avoided). In addition, the signal of the process control wirelesscommunication of which highly real-time responsiveness is required whileguaranteeing priority, and the signal of which real-time responsivenessis not required so much are allowed to coexist on the same network. Thesystem is therefore effective in respect of those points described asabove.

(Additional Claim 1)

A control network management system for relaying a first wirelesscommunication in conformity with IP (Internet Protocol), and a processcontrol wireless communication standard, and a second wirelesscommunication in conformity with IP, and a wireless communicationstandard differing from the standard, the control network managementsystem comprising a first repeater having a packet control means forwriting priority information in a TOS (Type of Service) field of theheader of communication packet data of the first wireless communication,and calculating a hash value of the header, before transmitting thecommunication packet data with the hash value added thereto, a secondrepeater having a packet control means for deleting priority informationin a TOS field of the header of communication packet data of the secondwireless communication, or changing the priority information to priorityinformation lower in priority than the priority information given to theTOS field by the packet-control means of the first repeater, andcalculating a hash value of the header before transmitting thecommunication packet data with the hash value added thereto, and a thirdrepeater comprising a correctness-inspection means for inspectingcorrectness on the basis of a hash value of the communication packetdata of the first wireless communication, or the second wirelesscommunication, received from the first repeater, or the second repeater,respectively, and a priority-control means for applying priority controlto the header of the communication packet data received from the firstrepeater, or the second repeater, respectively, on the basis of priorityinformation, thereby transmitting correct communication packet data thatis high in priority to a control system.

(Additional Claim 2)

The control network management system according to claim 1, wherein thepacket control means of the first repeater writes priority informationhigher in priority than the priority information given to the TOS fieldby the packet-control means of the third repeater, in the communicationpacket data of the first wireless communication, and the packet controlmeans of the second repeater writes priority information lower inpriority than the priority information given to the TOS field by thepacket-control means of the first repeater, in the communication packetdata of the second wireless.

(Additional Claim 3)

The control network management system according to any of claims 5 to 7,wherein the correctness-inspection means of the third repeater inspectscorrectness depending on whether or not received communication packetdata of the first wireless communication, or the second wirelesscommunication is received by the third repeater itself after a lapse ofpredetermined time from the time stamp written in the respectivecommunication packet data.

The control network management system according to the invention iseffective in that the control network management system is provided withthe first repeater having the packet control means for writing priorityinformation in the header of the communication packet data of the firstwireless communication, as received, and transmitting the communicationpacket data with the hash value of the header, added thereto, the secondrepeater having the packet control means for zero-clearing part, or thewhole of priority information in the header of the communication packetdata of the second wireless communication, as received, or changing thepriority information to the predetermined value before transmitting thecommunication packet data with the hash value of the header, addedthereto, and the third repeater having the priority control means forapplying priority control to the headers of respective communicationpacket data blocks received from the first repeater or the secondrepeater, on the basis of the priority information, thereby transmittingthe communication packet data to the control system, so that it ispossible to prevent the tampering on the header of communication packetdata, and the tampering attack on signal priority, thereby forestallingthe replay attack (tampering, and so forth, attempted by the mala fidethird party, can be avoided), and furthermore, the signal of the processcontrol wireless communication of which highly real-time responsivenessis required while guaranteeing priority, and the signal of whichreal-time responsiveness is not required so much are allowed to coexiston the same network.

While the present invention has been shown and described with referenceto certain exemplary embodiments thereof, other implementations arewithin the scope of the claims. It will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims.

1. A control network management system for relaying a first wirelesscommunication in conformity with IP (Internet Protocol) and a processcontrol wireless communication standard, and a second wirelesscommunication in conformity with IP, and a wireless communicationstandard differing from the standard, the control network managementsystem comprising: a first repeater having a packet control means forwriting priority information in a header of communication packet data ofthe first wireless communication, as received and transmitting thecommunication packet data with a hash value of the header, addedthereto; a second repeater having a packet control means forzero-clearing part, or a whole of priority information in a header ofcommunication packet data of the second wireless communication, asreceived, or changing the priority information to a predetermined valuebefore transmitting the communication packet data with a hash value ofthe header, added thereto; and a third repeater having a prioritycontrol means for applying priority control to the header of thecommunication packet data received from the first repeater or the secondrepeater, on the basis of priority information, thereby transmitting thecommunication packet data to a control system.
 2. The control networkmanagement system according to claim 1, wherein the packet control meansof the second repeater changes the priority information in the header ofthe communication packet data of the second wireless communication topriority information lower in priority than the priority informationwritten in the header of communication packet data of the first wirelesscommunication by the packet control means of the first repeater.
 3. Thecontrol network management system according to claim 1, wherein thethird repeater comprises a correctness-inspection means for inspectingcorrectness on the basis of a hash value of the communication packetdata received from the first repeater or the second repeater, therebytransmitting correct communication packet to the control system.
 4. Thecontrol network management system according to claim 1, furthercomprising a fourth repeater, the fourth repeater comprising apriority-control means for executing priority control on the basis ofthe priority information in the header of the communication packet datareceived from the third repeater, and a correctness-inspection means forinspecting correctness on the basis of a hash value of the communicationpacket data, thereby transmitting correct communication packet data tothe control system.
 5. The control network management system accordingto claim 1, wherein the first repeater comprises a time-stamp controlmeans for, upon receiving the communication packet data of the firstwireless communication, adding a time-stamp field to the header of thecommunication packet data, thereby writing a time-stamp therein; thesecond repeater comprises a time-stamp control means for, upon receivingthe communication packet data of the second wireless communication,adding a time-stamp field to the header of the communication packetdata, thereby writing a time-stamp therein; and thecorrectness-inspection means of the third repeater inspects correctnessof the communication packet data on the basis of the time-stamp writtenin the communication packet data of the first wireless communication, orthe second wireless communication, as received.
 6. The control networkmanagement system according to claim 1, wherein the packet-control meansof the second repeater as well as the first repeater write arecalculated checksum of the header of the respective headers of thecommunication packet data, and the correctness-inspection means of thethird repeater inspects matching property of communication packet data,on the basis of the respective checksums written in the communicationpacket data of the respective wireless communications, as received,thereby transmitting communication packet data having the matchingproperty, to the control system.
 7. The control network managementsystem according to claim 4, wherein: the third repeater comprises atime-stamp control means for, upon receiving communication packet data,adding a time-stamp field to the header of the communication packetdata, and writing a time-stamp therein; and the packet-control means forwriting the recalculated checksum of the header in the respectiveheaders of the communication packet data while thecorrectness-inspection means of the fourth repeater may inspectcorrectness of the communication packet data, on the basis of the timestamp written in the communication packet data of the wirelesscommunication, received from the third repeater, further inspectingmatching property of the communication packet data, on the basis of thechecksum written in the communication packet data of the respectivewireless communications, as received, before transmitting communicationpacket data having the matching property to the control system.
 8. Thecontrol network management system according to claim 5, wherein: thethird repeater comprises a time-stamp control means for, upon receivingcommunication packet data, adding a time-stamp field to the header ofthe communication packet data, and writing a time-stamp therein; and thepacket-control means for writing the recalculated checksum of the headerin the respective headers of the communication packet data while thecorrectness-inspection means of the fourth repeater may inspectcorrectness of the communication packet data, on the basis of the timestamp written in the communication packet data of the wirelesscommunication, received from the third repeater, further inspectingmatching property of the communication packet data, on the basis of thechecksum written in the communication packet data of the respectivewireless communications, as received, before transmitting communicationpacket data having the matching property to the control system.
 9. Thecontrol network management system according to claim 6, wherein: thethird repeater comprises a time-stamp control means for, upon receivingcommunication packet data, adding a time-stamp field to the header ofthe communication packet data, and writing a time-stamp therein; and thepacket-control means for writing the recalculated checksum of the headerin the respective headers of the communication packet data while thecorrectness-inspection means of the fourth repeater may inspectcorrectness of the communication packet data, on the basis of the timestamp written in the communication packet data of the wirelesscommunication, received from the third repeater, further inspectingmatching property of the communication packet data, on the basis of thechecksum written in the communication packet data of the respectivewireless communications, as received, before transmitting communicationpacket data having the matching property to the control system.